ctrl_iface: Retain legacy ctrl interface directory

The ctrl_interface format as ctrl_<ifname> seems not necessary.
For bridged SAP case, the interface name is different already.
For Multi-Link SAP case, upstream hostapd already implemented
link level socket with commit
14cb3906af0a53547019d3b2c68fc4f2fca41f5a. Also, this
ctrl_<ifname> format causes unexpected failure when using
"hostapd_cli" without any parameter in legacy cases.

Retain legacy ctrl interface to fix that.

Bug: 395521142
Test: Manual test, single band & dual band hotspot works normally.
Change-Id: I840c03aa0a171b155c1d0f60b5ca25431de2d9e7
1 file changed